Интегральные усилители — Octave Audio V 70 CLASS A

In the V 70 Class A, Octave Audio of Karlsbad in Germany combines a valve integrated layout with pentode output valves in push-pull, biased in Class A. Octave offers a phono board for MM or MC cartridges as an option. Standard output valves are four KT 88 with a carbon coating, and four KT 120 are offered as an option. Silver and black finishes are available.

Key specs that matter

Output reaches 2 x 50 W RMS into 4 ohm and 2 x 70 W peak on the High power setting, and on Low 2 x 25 W RMS and 2 x 35 W peak. Into 8 ohm output drops by 20 percent. Frequency response is 20 Hz to 70 kHz at 50 W within -1 and -3 dB. At 10 W into 4 ohm distortion measures 0.1 percent, while the signal to noise figure is -100 dB at 50 W unweighted and -110 dB weighted. Overall gain is 35 dB, and the damping factor is 5 into 8 ohm. Input impedance is 50 kohm on RCA and 25 kohm on XLR with 300 mV sensitivity. The amplifier measures 451 x 150 x 415 mm and weighs 22.1 kg. Consumption is 350 W at full power, 190 W idle and 20 W in ECO mode.

Engineering and use context

One ECC83 and two ECC81 valves form the driver section. KT 120 or KT 150 valves are required for the High power setting, while KT 88 or 6550 types run on Low. An auto bias circuit adjusts itself to the fitted valves and shows its state on coloured LEDs, so no manual trimmers are needed. Octave calls this Dynamic Bias Control. The grid 2 voltage is 340 V. Crosstalk between inputs is -105 dB, and channel separation is 55 dB. The wideband output transformers use PMX cores of silicon steel. Operation without load is stable, and the amplifier is protected against operation without speakers. ECO mode shuts the valve section down after about 7 minutes without a signal, and a soft start delays power-up by 20 to 30 seconds. Inrush current is limited to 600 W for 0.3 seconds. With the Super Black Box power supply, peak output reaches its full rating.

Pairing

Inputs are six RCA, one of them a home theatre bypass and one assignable to the phono board, plus one XLR. Outputs include an adjustable regulated preamplifier output for a subwoofer, with a maximum of 5 V RMS and 240 ohm output impedance, an RCA record output and one pair of speaker terminals. Octave gives an optimal load range of 4 to 16 ohm, and a remote control is supplied.

Alternatives

The Octave V 110 SE is a push-pull pentode integrated amplifier from the same range rated at 2 x 110 W RMS into 4 ohm.